JP2002280207A - Electromagnetic wave absorption heat conducting composition, thermal softness electromagnetic wave absorption heat-dissipating sheet and heat-dissipating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electromagnetic wave absorption heat conducting composition which is superior in heat-dissipating performance and electromagnetic wave absorbability, and a thermal softness electromagnetic wave absorbent heat-dissipating sheet obtained by forming it into a sheet-like form. SOLUTION: An electromagnetic wave absorption heat conducting composition is a heat conducting composition for forming an electromagnetic wave absorption heat-dissipating member, in which heat generates by operation to be higher than room temperatures, and which is disposed between heat generating electronic components as an electromagnetic wave generation source and heat- dissipating parts. It is non-fluid in a state of room temperatures prior to operation of electronic parts and is converted into low viscosity, softened or melted due to heat generation, when electronic components are operated, so that at least the surface is fluidized. Thus, a gap is filled between the electronic components and the heat-dissipating parts, without substantially an opening gap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-generating electronic component which generates heat when operated and has a temperature higher than room temperature and can be a source of electromagnetic waves, and a heat dissipating member (heat dissipating component) such as a heat sink or a circuit board. An electromagnetic wave absorbing heat conductive composition and a heat softening electromagnetic wave absorbing heat radiating sheet for forming an electromagnetic wave absorbing heat radiating member arranged for cooling an electronic component and absorbing electromagnetic waves by heat conduction, and a heat radiation construction method About.

[0002]

2. Description of the Related Art The circuit design of modern electronic devices, such as televisions, radios, computers, medical instruments, office machines, and communication devices, has become increasingly complex. For example, integrated circuits containing hundreds of thousands of transistors have been manufactured for these and other devices. With this increasing design complexity, smaller electronic components are being manufactured, and the ability to incorporate more and more of these components in increasingly smaller device areas is increasing, as well as device Dimensions continue to shrink.

[0003] For this reason, since a failure or malfunction occurs due to heat generated from each component, a method for effectively dissipating heat generated from electronic components is required.

On the other hand, in the case of electronic components, particularly LSIs such as CPUs, drivers, ICs, and memories used in electronic devices such as personal computers, digital video disks, and cellular phones, the above-described heat generation is accompanied by the improvement in the degree of integration. At the same time, the occurrence of harmful electromagnetic waves, such as failures, malfunctions, malfunctions, or effects on the human body due to interference between electronic components due to the shift to higher frequencies for higher performance Is a problem.

[0005] In order to reduce the heat generated from electronic components, many heat dissipating methods, heat dissipating members and compositions for use therein have been proposed. 2. Description of the Related Art Conventionally, in electronic devices and the like, a heat sink using a metal plate having high thermal conductivity such as brass has been used in order to suppress a rise in temperature of electronic components during use. The heat sink conducts heat generated by the electronic component and releases the heat from the surface due to a temperature difference from the outside air.

In order to efficiently transfer the heat generated from the electronic components to the heat sink, the heat sink must be in close contact with the electronic components. However, since there is a difference in height between the electronic components and tolerance due to the assembling process, flexibility is required. A heat conductive sheet having thermal conductivity and a heat conductive grease are interposed between the electronic component and the heat sink, and heat conduction from the electronic component to the heat sink is realized through the heat conductive sheet or the heat conductive grease. . As the heat conductive sheet, a heat conductive sheet (heat conductive silicone rubber sheet) formed of heat conductive silicone rubber or the like is used, but these sheets have a problem in interfacial heat resistance.

Therefore, as a method of reducing the interfacial thermal resistance, a heat conductive grease or a heat softening sheet as described in JP-T-2000-509209 has been proposed. However, these are all limited to heat dissipation members and do not have electromagnetic wave absorption performance.

On the other hand, many attempts have been made to shield electromagnetic waves generated from electronic components. Generally, metal, plating or many using a conductive composition,
These all use the function of reflecting electromagnetic waves. A sheet member filled with an organic rubber, in particular, a soft magnetic powder or a ferrite having a medium of chlorinated polyethylene as an electromagnetic wave absorbing component is already on the market. However, these sheets were rigid and had electromagnetic wave shielding ability, but were ineffective at dissipating heat.

Further, recently, materials having both heat conduction and electromagnetic wave absorption have been proposed. For example, JP-A-11-335
No. 472 discloses that Mn-Z
It has been proposed that a sheet-like structure containing ferrite such as n-ferrite and Ni-Zn ferrite can provide a noise suppressing effect. However, the sheet is hardened due to the filling of the electromagnetic wave absorbing filler, and has a low thermal conductivity, which is not sufficient as a heat dissipating member.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an electromagnetic wave absorbing heat conductive composition having excellent heat radiation performance and excellent electromagnetic wave absorbing property for suppressing generation of electromagnetic noise, and formed into a sheet shape. It is an object of the present invention to provide a heat-softening electromagnetic wave absorbing heat radiation sheet and a heat radiation construction method.

[0011]

Means for Solving the Problems and Embodiments of the Invention As a result of diligent studies to achieve the above object, the present invention contains an electromagnetic wave absorbing filler, is solid at ordinary temperature, and has a certain temperature range. By using an uncured composition that can be heat-softened, reduced in viscosity or melted, and easily formed into a required shape including a sheet, between a heat-generating electronic component and a heat-radiating component (boundary), Electromagnetic waves that can be easily attached to and detached from electronic components and heat sinks, are softened by the heat generated during the operation of electronic components and reduce the interfacial contact thermal resistance, thereby improving heat dissipation performance and suppressing electromagnetic noise. It was found to be excellent in absorbency.

That is, a component which is solid at room temperature and which is softened, reduced in viscosity or melted in a certain temperature range is selected, and a filler having electromagnetic wave absorbing performance is filled into this component, and if necessary, further heat conduction is performed. It has been found that by arranging the composition filled with the conductive filler between the heat-generating electronic component and the heat-dissipating component (boundary), it is possible to achieve desired electromagnetic wave absorption performance and heat dissipation. It has been reached.

Therefore, according to the present invention, the heat generated by the operation is raised to a temperature higher than the room temperature, and the heat for forming the electromagnetic wave absorbing heat radiating member disposed between the heat generating electronic component serving as the electromagnetic wave generating source and the heat radiating component. A conductive composition, which is non-flowable at room temperature prior to the operation of the electronic component, and has a low viscosity, softens or melts due to heat generated during the operation of the electronic component, and at least the surface is fluidized, whereby the electronic component and Provided is an electromagnetic-wave-absorbing heat-conducting composition characterized by being filled with substantially no gap between the heat-radiating component and the heat-radiating component. The present invention also provides a heat-softening electromagnetic wave-absorbing heat radiation sheet in which the composition is formed into a sheet. Further, the present invention is characterized in that the device generates heat by operating to a temperature higher than room temperature, and arranges the electromagnetic wave absorbing heat conductive composition between a heat generating electronic component serving as an electromagnetic wave generating source and a heat radiating component; By operating the electronic component to generate heat, the composition is reduced in viscosity, softened or melted to fluidize at least the surface thereof, and the composition is formed from at least one of the exothermic electronic component and the heat radiating component. There is provided a method for applying an electromagnetic wave absorbing heat conductive composition, characterized in that it is pressed and filled substantially without gaps between the electronic component and the heat radiating component.

Hereinafter, the present invention will be described in detail. The electromagnetic wave-absorbing heat conductive composition of the present invention operates, in particular, reaches a temperature higher than room temperature by applying a voltage, and is located (boundary) between a heat-generating electronic component and a heat-radiating component that can be a source of electromagnetic waves. A composition used as an electromagnetic wave-absorbing heat-radiating member to be arranged, which does not have fluidity in a normal room temperature state before the operation of electronic components, and is held in a state of a molded article such as a sheet or a base material or the like. Maintained in a state where it can be transported, lowering viscosity due to heat generated during operation of electronic components,
The boundary between the electronic component and the heat radiating component is substantially filled by softening or melting, and in this case, preferably, when the electronic component generates heat, a pressure is applied from at least one of the electronic component and the heat radiating component, so that the electronic component and the heat radiating component are pressed. It is filled at the boundary with the heat radiating component.

[0015] The electromagnetic wave absorbing heat conductive composition of the present invention contains an organic binder component and an electromagnetic wave absorbing filler, and when thermal conductivity is required, these components and the heat conductive filler. Is preferred. Hereinafter, the method for producing each of these components and the composition will be described in detail.

Organic Binder Component The organic binder component which can serve as a medium (matrix) of the electromagnetic wave absorbing heat conductive composition of the present invention is a solid which is substantially solid at ordinary temperature, and preferably has a heat generation at 40 ° C. or higher. In the temperature range of not more than the highest temperature due to heat generation of the conductive electronic component, specifically, in a temperature range of about 40 to 100 ° C., particularly about 40 to 90 ° C., at least the surface is fluidized due to heat softening, low viscosity or melting. Any material may be used as long as it is used, and the temperature range during operation of α-olefin, silicone resin, wax, wax, etc., preferably 40 to 100 ° C.
A substance having a melting point (hereinafter, referred to as a low-melting point substance), which does not have a melting point in the above-mentioned operating temperature range, but becomes soft or low-viscosity at the operating temperature (hereinafter, referred to as a low-melting substance). , Which is referred to as a heat fluidizing substance), a syrupy substance in the above operating temperature range, or a thermoplastic resin having a melting point at a temperature higher than the operating temperature range or having essentially no melting point and / or A mixture of a thermosetting resin and the above-mentioned low-melting substance, a heat-fluidizing substance or a syrup-like substance (the composition softens as a whole) and the like, and a thermoplastic resin and / or a thermosetting resin and a low-melting substance, Mixtures with heat fluidizing substances or syrupy substances are preferred.

In this case, the organic binder includes one or more of a polyolefin polymer, an acrylic polymer, a fluorine polymer, and a siloxane polymer, and the composition flows out as a liquid. However, it is preferable to include a low-melting substance, a heat-fluidizing substance, or a syrup-like substance so as to cause thermal softening, low viscosity, or melting. If flame retardancy is required, a fluoropolymer,
It is preferable to include a siloxane-based polymer. In the case of a fluoropolymer, a liquid fluororesin is preferable, and a copolymer of hexafluoropropene / vinylidene fluoride / tetrafluoroethylene is particularly preferable. In the case of a siloxane-based polymer, it is a solid at room temperature, such as silicone resin, and softens, lowers in viscosity or melts when heated,
Examples thereof include those having a melting point at room temperature or higher, such as an alkyl-modified silicone, and those containing a silicone resin are preferable. Polymers containing RSiO _3/2 units and / or SiO ₂ units to maintain non-flowability at room temperature, or copolymers of these with R ₂ SiO units (silicone resins), silicone resins and linear poly A suitable material is a mixture with siloxane (silicone raw rubber, silicone oil) (R is a monovalent hydrocarbon group).

As described above, in order to cause a critical decrease in viscosity, it is desirable that the composition contains an oligomer or wax having a relatively low polymerization degree. Specifically, low-melting substances such as α-olefins, waxes, waxes, acrylic oligomers, silicone resins, and fluorine-based oligomers, heat-fluidizing substances, and syrup-like substances are used. In this case, the low melting point substance and the heat fluidizing substance preferably have a melting point or a softening point between 40 and 100 ° C.

In the present invention, in particular, polyolefins (preferably EP, EPD) having no melting point in the above operating temperature range.
M) a polymer, an acrylic polymer, a fluorine-based polymer or a siloxane-based polymer;
A mixture of a substance having a melting point in the above-mentioned operating temperature range, such as wax, wax, silicone resin, or the like, is preferable.

The compounding ratio is not particularly limited as long as the composition is solid at room temperature, fluidized by the heat generated during the operation of the electronic component, and can be filled without voids. %, Especially 20 to 80
% By weight.

As the organic binder component of the present invention, those which impart flexibility and tackiness to the composition of the present invention (necessary from the necessity of temporarily fixing a heat radiating sheet to an electronic component or a heat sink) are given. It is preferable that a polymer having a single viscosity or the like may be used. However, when two or more polymers having different viscosities are mixed and used, a good balance between flexibility and tackiness is obtained. Since it is advantageous since a sheet can be obtained, it is preferable to use two or more kinds having different viscosities.

The above-mentioned polymer or composition is preferably heat-softened or melted and then crosslinked, whereby the reworkability can be improved. That is, after the present composition adheres to the heat-generating electronic component and the heat-dissipating component by softening once, it follows the expansion and shrinkage due to heat while maintaining low thermal resistance by crosslinking, and when rework is required. , Which can be easily peeled off from the electronic component and the heat radiating component by being crosslinked.
Therefore, from this point, it is preferable that the present composition be curable by a crosslinking reaction.

For such a purpose, it is preferable that the polymer has a curing reactive functional group at a terminal or a side chain. Such functional groups are usually OH, COO in polyolefin resin and acrylic resin.
H, aliphatic unsaturated groups, glycidyl groups, norbornene groups and the like. In a fluorine-based resin, a CH group or the like of a vinylidene fluoride group can be used for crosslinking, and in a siloxane-based polymer, an aliphatic unsaturated group, a silanol group, an alkoxysilyl group, or the like can be used for crosslinking.

Electromagnetic Wave Absorbing Filler The electromagnetic wave absorbing filler used in the present invention is preferably at least one selected from metal-based ferromagnetic powders and oxide-based ferromagnetic powders. The magnetic powder and the oxide-based ferromagnetic powder may be used alone or as a mixture.

As the metal-based ferromagnetic powder, iron and an alloy containing iron are preferable. As a ferromagnetic iron alloy, Fe-N
i-based, Fe-Co-based, Fe-Cr-based, Fe-Si-based, F
e-Al system, Fe-Cr-Si system, Fe-Cr-Al
System, Fe-Al-Si system, Fe-B-Si system, Ni-F
An e-based, Co-Fe-Ni-Si-B-based magnetic alloy or the like can be used. These metal-based ferromagnetic powders may be used alone or in a combination of two or more.

The shape of the metallic magnetic powder may be flat or particulate, but it is preferable to use the flat shape because of its good electromagnetic wave absorption performance. When a flat metal-based soft magnetic powder is used, the filling amount tends to be small, so that a particulate metal-based soft magnetic powder may be used in combination.

In this case, the size of the flat powder is as follows:
Average maximum length is 0.1 to 350 μm, especially 0.5 to 10
Those having a thickness of 0 μm and an aspect ratio of 2 to 50 are preferred. In the case of particulate powder, the average particle size is 0.1 to 10
It is preferable to use those having a thickness of 0 μm, particularly 0.5 to 50 μm.

As the oxide-based ferromagnetic powder, ferrite
Is preferred. Specifically, as ferrite, ZnFe_Two
O_Four, MnFe_TwoO_Four, MgFe_TwoO_Four, CoFe_TwoO_Four, N
ife _TwoO_Four, CuFe_TwoO_Four, Fe_ThreeO_Four, Cu-Zn-F
Ferrite, Ni-Zn-ferrite, Mn-Zn-ferrite
Spinel ferrite with basic composition of light, Ba_Two
Co_TwoFe₁₂O_{twenty two}, Ba_TwoNi_TwoFe₁₂O_{twenty two}, Ba_TwoZn_Two
Fe₁₂O_{twenty two}, Ba_TwoMn_TwoFe₁₂O_{twenty two}, Ba_TwoMg_TwoFe₁₂
O_{twenty two}, Ba_TwoCu_TwoFe₁₂O_{twenty two}, Ba_ThreeCo_TwoFe_{twenty four}O₄₁To
Ferrox sprayer (Y type, Z type) type with basic composition
Hexagonal ferrite, BaFe₁₂O₁₉, SrFe₁₂O₁₉Passing
And / or BaFe₁₂O₁₉, SrFe₁₂O₁₉The Fe element
Replaced with Ti, Co, Mn, Cu, Zn, Ni, Mg
Magneplumbite (M type) type 6
For example, tetragonal ferrite can be used. These fe
Light may be used alone or in combination of two or more.
They may be used together.

The shape of the oxide magnetic powder is as follows.
Either a flat shape or a particulate shape may be used, but it is preferable to use a flat shape from the viewpoint of a large surface area. When a flat oxide-based magnetic powder is used, the filling amount tends to be small, so that a particulate oxide-based magnetic powder may be used in combination.

In this case, the size of the flat powder is as follows:
Average maximum length is 0.1 to 350 μm, especially 0.5 to 10
Those having a thickness of 0 μm and an aspect ratio of 2 to 50 are preferred. In the case of particulate powder, the average particle size is 0.1 to 10
It is preferable to use those having a thickness of 0 μm, particularly 0.5 to 50 μm.

The compounding amount of these electromagnetic wave absorbing fillers is 100 to 300 parts by weight based on 100 parts by weight of the organic binder component.
0 parts by weight, preferably 150 to 1600 parts by weight. If the amount of the electromagnetic wave absorbing filler is too small, the electromagnetic wave absorbing performance may not be sufficient.If the amount is too large, heat softening at the time of heat generation, low viscosity, insufficient fluidity at the time of melting, and room temperature Since the composition is hard and brittle, sheet forming may be difficult.

Heat conductive filler The heat conduction effect is poor only by the combination of the above medium and the electromagnetic wave absorbing filler. If a further heat dissipation effect is required, the heat conductive filler is combined with the above components. Can be used.

Examples of the thermally conductive filler used in the present invention include non-magnetic metals such as copper and aluminum, metal oxides such as alumina, silica, magnesia, bengalah, beryllia, titania, zirconia, aluminum nitride, and nitride. Materials generally used as a thermally conductive filler, such as metal nitrides such as silicon and boron nitride, artificial diamond and silicon carbide, can be used. These heat conductive fillers may be used alone or in a combination of two or more.

These thermal conductive fillers have an average particle size of 0.1 to 100 μm, particularly 0.1 μm, similarly to the electromagnetic wave absorbing filler.
It is preferable to use one having a thickness of 5 to 50 μm. Further, the shape is desirably spherical, and it may be used alone or as a mixture of a plurality of different shapes. In order to improve the thermal conductivity, it is recommended to use two or more kinds of particles having different average particle diameters so as to make the composition close to close packing.

The amount of the thermally conductive filler is preferably 10 to 2500 parts by weight, more preferably 1000 to 2000 parts by weight, based on 100 parts by weight of the organic binder component. If the amount of the heat conductive filler is too small, the heat conductivity may be insufficient. If the amount is too large, the sheet processability and workability may be deteriorated.

Other Additives The electromagnetic wave absorbing heat conductive composition of the present invention may further contain, as optional components, additives, fillers and the like usually used in synthetic rubbers as long as the objects of the present invention are not impaired. . Specifically, silicone oil as a release agent, such as fluorine-modified silicone surfactant,
Colorants such as carbon black, titanium dioxide and red iron, flame retardants such as halogen compounds, phosphorus compounds, platinum catalysts, etc., usually rubber as a processability improver, process oils used when compounding plastics, reactive silanes or siloxanes, A reactive titanate catalyst, a reactive aluminum catalyst or the like can be added.

Production Method The method for producing the electromagnetic wave absorbing heat conductive composition of the present invention uses a rubber kneader such as a two-roll mill, a Banbury mixer, a dough mixer (kneader), a gate mixer, and a planetary mixer. In some cases, it can be obtained by mixing uniformly by heating.

The method for producing the heat-softening electromagnetic wave-absorbing heat-dissipating sheet includes extruding, kneading, calendering, roll-forming, press-molding the kneaded composition, dissolving in a solvent, and coating. Thereby, it can be obtained by molding into a sheet.

The thermal conductivity of the obtained electromagnetic wave absorbing heat conductive composition and heat softening electromagnetic wave absorbing heat radiation sheet was 0.5 W /
mK or more, preferably 1 to 20 W / mK. If the thermal conductivity is less than 0.5 W / mK, the thermal conductivity between the electronic component and a heat radiating component such as a heat sink will be low, and sufficient heat radiating performance may not be exhibited.

The viscosity of the above composition and sheet at 80 ° C. is preferably 1 × 10 ² to 1 × 10 ⁵ Pa · s, and more preferably 5 × 10 ^{2 to} 5 × 10 ⁴ Pa · s.
If the viscosity is less than 1 × 10 ² Pa · s, it may flow out from between the electronic component and a heat radiating component such as a heat sink.
If it exceeds × 10 ⁵ Pa · s, the contact thermal resistance may be increased, and the thermal conductivity between the electronic component and a heat radiating component such as a heat sink may be reduced, and sufficient heat radiating performance may not be exhibited. .

Further, the plasticity (JIS K 6200) at 25 ° C. of the above composition and sheet is 100 to 70.
0, and preferably in the range of 200 to 600. If the degree of plasticity at 25 ° C. is less than 100, the mountability to electronic components may be poor, and if it exceeds 700, the sheet workability and the mountability to electronic components may be poor.

The thus obtained electromagnetic wave absorbing heat conductive composition and heat softening sheet can be easily attached to and detached from heat radiating components such as electronic components and heat sinks. By viscous, softening or melting, the thermal resistance at the interface between the electronic component and the heat radiating component is reduced, so that the heat radiation performance is excellent and the electromagnetic wave absorbing property for suppressing the generation of electromagnetic wave noise is excellent.

In this case, the composition or sheet generates heat by operation to reach a temperature higher than room temperature, and is arranged between the heat-generating electronic component serving as an electromagnetic wave generation source and the heat radiation component. At this time, the composition or sheet and the electronic component do not completely adhere to each other, and have a minute gap, but the composition or sheet is softened, reduced in viscosity or melted by the heat generated by the operation of the electronic component. At least the surface is fluidized,
The micro voids are filled so as to be in close contact with the electronic component, and the interface contact thermal resistance is reduced as described above. In this case, it is preferable to apply a pressing force to the composition or sheet from at least one of the electronic component and the heat radiating component to secure better adhesion.

The type of the heat-generating electronic component is not particularly limited, and the composition of the present invention is applied to a heat-generating electronic component such as a personal computer which generates an electromagnetic wave by applying a voltage and generates heat. Or a sheet is effective.

[0045]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 4] The softening point of a mixture mainly composed of an acrylic resin and an electromagnetic wave absorbing filler was 4
A heat-softening electromagnetic-wave-absorbing heat-dissipating sheet in which an acrylic heat-conductive electromagnetic-wave-absorbing composition at 0 ° C. or higher was formed in a sheet shape was produced by the following procedure.

An acrylic resin was used as the resin component of the acrylic heat conductive electromagnetic wave absorbing composition, and paraffin wax was used as the heat softening component. As other ingredients,
Carbon functional silane was used as a surface treatment agent for the electromagnetic wave absorbing filler and the thermally conductive filler. The following shows the ingredients of the compounding ingredients.

Description of Raw Materials 1) Paraffin wax, paraffin wax 115
(Melting point 47 ° C.), paraffin wax 130 (melting point 55)
2) Acrylic resin, SK Dyne 1310 (non-volatile content 32)
３４34%, the remainder is solvent), trade name of Soken Chemical Co., Ltd. 3) Powder surface treating agent: carbon functional silane, KBM-3103, trade name of Shin-Etsu Chemical Co., Ltd. 4) Thermal conductive filler : Alumina powder, AS30, trade name of Showa Denko KK 5) Electromagnetic wave absorbing filler: Fe-Cr (metal-based soft magnetic spherical powder), PMIC-15, trade name of Daido Steel Co., Ltd. 6) Electromagnetic wave Absorbent filler: Fe-Cr (metallic soft magnetic flat powder), PMIC-15F, trade name of Daido Steel Co., Ltd.

Preparation procedure of heat softening electromagnetic wave absorbing heat radiation sheet
And raw materials of formulations shown in the performance evaluation in Table 1 were charged into a homogenizer (stirred dissolver), it was mixed and stirred at room temperature for 1 hour. After coating the obtained solution on a PET film coated with a release agent using a comma coater, in an atmosphere of 100 ° C.,
By heating for 10 minutes, the solvent component (volatile content) was removed, and a sheet having a width of 300 mm and a thickness of 0.5 mm was produced.

The obtained heat-softening electromagnetic-wave-absorbing heat-dissipating sheet is punched and formed into a predetermined shape, the PET film is peeled off, and then the noise attenuation rate, plasticity, thermal conductivity, thermal resistance,
The viscosity and the heat softening point were measured by the following evaluation methods. 1) Noise attenuation measurement method: FIG. 1 shows a measurement block diagram.

In the anechoic chamber 1, the heat-softening electromagnetic wave-absorbing heat radiation sheet of the present invention (width 30 mm, length 30 mm, thickness 0.3 mm).
5 mm) with a CPU (operating frequency 533 MHz) and Al
The PC 2 sandwiched between the heat sinks was installed, and the receiving antenna 3 was installed at a position 3 m away from the PC 2. That is, it conforms to the FCC-compliant 3m method. In FIG. 1, reference numeral 4 denotes a display, and 5 denotes a keyboard. Next, the PC 2 is activated, and the generated noise is transmitted to the EMI in the shield room 6 connected to the receiving antenna 3.
The measurement was performed by a receiver (spectrum analyzer) 7. At the time of measurement, the display 4 connected to the PC 2
Is turned off to prevent reception of noise from the display 4. 2) Plasticity measurement method: Measured by a plasticity test according to JIS K6249. 3) Thermal conductivity measuring method: Thermal conductivity measuring instrument QTM-500
(Kyoto Denki brand name). 4) Thermal resistance measurement method: A 0.5 mm thick sample punched into a transistor TO-3 type shape was
SD923 (trade name of Fuji Electric) and heat sink FBA
-150-PS (trade name, manufactured by OS Co., Ltd.) and a load of 300 gf / cm ² was applied. The heat sink was placed in a constant temperature water bath and kept at 60 ° C. Next, 10 V and 3 A power is supplied to the transistor, and after 5 minutes, the temperature of the thermocouple embedded in the transistor (temperature T ₁ ) and the heat sink (temperature T ₂ ) is measured, and the thermal resistance Rs of the sample is calculated from the following equation. (° C./W) was calculated. Rs = (T ₁ −
T ₂ ) / 305) Viscosity measurement method: Measured with an ARES viscoelastic system (manufactured by Rheometric Scientific). 6) Measurement method of thermal softening point: Measured by a Vicat softening temperature test method of JIS K7206.

In addition, sheet workability, flexibility, tackiness,
The handleability was evaluated according to the following criteria. The results are shown in Table 1. Evaluation criteria Sheet workability: Extrusion moldability was evaluated. Flexibility: Evaluated by the state of crack generation when the sheet was bent at 90 °. Tackability: As shown in FIG. 2, it was placed on the surface of the heat sink 11 and left in the air for 5 minutes so that the heat radiation sheet 12 was on the lower side, and evaluated by the presence or absence of peeling and falling off. Handleability: The attachment to the heat sink was performed manually and evaluated. ◎: Excellent ○: Good △: Somewhat good ×: Poor

[0053]

[Table 1]

[Examples 5 to 8] The softening point of a mixture containing a fluororesin and an electromagnetic wave absorbing filler as main components was 40.
A heat-softening electromagnetic-wave-absorbing heat-dissipating sheet in which a fluororesin-based heat-conductive electromagnetic-wave-absorbing composition at a temperature of not less than ° C was formed in a sheet shape was produced by the following procedure.

A liquid fluororesin was used as the resin of the fluororesin-based thermally conductive electromagnetic wave absorbing composition, and a ternary resin composed of polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene was used as the heat softening component. . As other components, carbon functional silane was used as a surface treatment agent for the electromagnetic wave absorbing filler and the heat conductive filler. The following shows the ingredients of the compounding ingredients.

Description of Raw Materials 1) Kiner 9301 (thermal softening temperature 80 ° C.), trade name of Daikin Industries, Ltd. 2) Liquid fluororesin, G101, trade name of Daikin Industries, Ltd. 3) Surface treatment agent for powder: carbon Functional silane, KBM-3103, brand name manufactured by Shin-Etsu Chemical Co., Ltd. 4) Thermal conductive filler: alumina powder, AS30, brand name manufactured by Showa Denko KK 5) Electromagnetic wave absorbing filler: Fe-Cr ( Metallic soft magnetic spherical powder), PMIC-15, trade name of Daido Steel Co., Ltd. 6) Electromagnetic wave absorbing filler: Fe-Cr (metallic soft magnetic flat powder), PMIC-15F, Daido Special Steel ( Co., Ltd. product name

Preparation procedure of heat-softening electromagnetic wave absorbing heat radiation sheet
And the raw materials of the formulation shown in the performance evaluation table 2 were stirred and mixed by a kneader. The obtained compound is extruded with an extruder, and a sheet having a width of 300 mm and a thickness of 0.5 mm is subjected to PET.
Made on film.

The obtained heat-softening sheet was punched and formed into a predetermined shape, the PET film was peeled off, and the noise attenuation rate, heat conductivity, heat resistance, viscosity, and heat softening point were determined in Example 1.
It was measured in the same manner as in Further, sheet workability, flexibility, tackiness, and handleability were evaluated in the same manner as in Example 1. Table 2 shows the results.

[0059]

[Table 2]

Examples 9 to 18 and Comparative Example 1 A sheet of a silicone-based thermally conductive electromagnetic wave absorbing composition having a softening point of 40 ° C. or higher, comprising a mixture containing a silicone resin and an electromagnetic wave absorbing filler as main components, was prepared. A heat-softening electromagnetic-wave-absorbing heat-dissipating sheet formed into a shape was prepared by the following procedure.

As the heat softening component of the silicone-based heat conductive electromagnetic wave absorbing composition, CH ₃ SiO _3/2 , (CH ₃ ) ₂ S
_{iO, C 6 H 5 SiO 3/2} , (C 6 H 5) (CH 3) SiO,
Methylphenyl silicone resin, which is a copolymer formed by combining (C ₆ H ₅ ) ₂ SiO structural units, was used. Two kinds of vinyl group-containing dimethylpolysiloxanes having different viscosities were used as matrix components. As other components, an organopolysiloxane containing a silicon-bonded alkoxy group represented by the following general formula (1) was added as a surface treatment agent for the electromagnetic wave absorbing filler and the heat conductive filler.

[0062]

Embedded image (In the formula, R ¹ represents any one of CH _3, OH, R ²
Are Si (OCH ₃ ) ₃ , Si (OC ₂ H ₅ ) ₃ , Si (C
H ₃ ) ₂ OH or Si (CH ₃ ) ₂ NH ₂ . m represents an arbitrary integer of 1 or more and 100 or less. In addition, dimethyldiphenylpolysiloxane was used as an internal release agent in order to improve the releasability from the liner when the sheet was mounted. The following shows the ingredients of the compounding ingredients.

Description of Raw Materials 1) Thermal softening component: methylphenyl silicone resin CH
₃ SiO _3/2 , (CH ₃ ) ₂ SiO, C ₆ H ₅ SiO _3/2 ,
(C ₆ H ₅ ) (CH ₃ ) SiO, a copolymer formed by combining structural units of (C ₆ H ₅ ) ₂ SiO), having a softening temperature of 40
C. (Resin A) and 60.degree. C. (Resin B). 2) Matrix component: Two types of vinyl group-containing dimethylpolysiloxane are used. High viscosity component: raw rubber KE-76V
BS, product name manufactured by Shin-Etsu Chemical Co., Ltd. Low viscosity component: dimethyl oil containing 30000 cSt vinyl group, manufactured by Shin-Etsu Chemical Co., Ltd. 3) Surface treatment agent for powder: organopolysiloxane containing silicon-bonded alkoxy group, Shin-Etsu Chemical Industry Co., Ltd.
4) Internal release agent: dimethyldiphenylpolysiloxane,
KF-54, trade name of Shin-Etsu Chemical Co., Ltd. 5) Thermal conductive filler: alumina powder, AS30, trade name of Showa Denko KK 6) Thermal conductive filler: aluminum nitride powder, UM, Toyo Aluminum 7) Thermal conductive filler: silicon carbide powder, GP # 1000,
8) Electromagnetic wave absorbing filler: Fe-Cr (metallic soft magnetic spherical powder), PMIC-15, trade name of Daido Steel Co., Ltd. 9) Electromagnetic wave absorbing filler: Fe-Cr (metallic soft magnetic flat powder), PMIC-15F, trade name of Daido Steel Co., Ltd. 10) Electromagnetic wave absorbing filler: Mn-Zn ferrite (oxide soft magnetic flat powder), BSF547 11) Electromagnetic wave absorbing filler: Fe-Ni (metallic soft magnetic spherical powder), MHT Permalloy PC, Mitsubishi Steel Corporation 12) Electromagnetic wave absorbing filler: Fe -Cr-Si (metal-based soft magnetic spherical powder), MHT410L-3Si, trade name of Mitsubishi Steel Corporation In order to improve reworkability, heat-softening electromagnetic wave absorption is performed by the heat generated by the operation of the heat-generating electronic components. Heat dissipation sheet If cross-linking the recone matrix (Example 1
In 8), an organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms in one molecule, a platinum group metal-based catalyst, and an acetylene alcohol-based reaction control agent were further added and mixed.

Preparation procedure of heat-softening electromagnetic wave absorbing heat radiation sheet
And raw materials of formulations shown in performance evaluation Tables 3 and 4 were charged into a planetary mixer and stirred for 2 hours mixing at 120 ° C.. Next, the mixture was degassed and mixed with two rolls at room temperature, and the obtained compound was extruded into a sheet having a width of 100 mm and a thickness of 0.5 mm using an extruder. In the case where the silicone matrix is crosslinked (Example 18),
An organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms in one molecule, a platinum group metal-based catalyst and an acetylene alcohol-based reaction control agent
After adding at room temperature with this roll, width 100m with extruder
m, extruded to a thickness of 0.5 mm, and processed into a sheet.

The obtained heat-softening sheet was punched and formed into a predetermined shape, and the noise attenuation rate, heat conductivity, heat resistance, viscosity and heat softening point were measured in the same manner as in Example 1.
Further, sheet workability, flexibility, tackiness, and handleability were evaluated in the same manner as in Example 1. The results are shown in Tables 3 and 4.

[0066]

[Table 3]

[0067]

[Table 4]

As an evaluation of reworkability, a heat-softening electromagnetic wave-absorbing heat-dissipating sheet was set between the heat sink and the CPU, and after the CPU was operated for 3 hours, the heat-softening electromagnetic wave-absorbing heat-dissipating sheet was removed from the heat sink and CPU. Although the ease of removal was evaluated, in Example 18, the reworkability was improved by crosslinking the sheet, and the attached matter of the heat-softening electromagnetic wave absorbing heat-dissipating sheet was easily wiped off with a dry cloth. , Could be removed neatly.

[Examples 19 to 31, Comparative Examples 2 to 4] A polyolefin-based thermally conductive electromagnetic wave absorbing composition having a softening point of 40 ° C. or higher, comprising a mixture containing a polyolefin and an electromagnetic wave absorbing filler as main components, was prepared. A heat-softening electromagnetic-wave-absorbing heat-dissipating sheet formed in a sheet shape was produced by the following procedure.

The thermal softening component of the polyolefin-based thermally conductive electromagnetic wave absorbing composition is represented by the following general formula (2): CH ₂ ＣＨCH (CH ₂ ) _n CH ₃ (2) (n is 16 to 50) Was used. As the matrix component, ethylene / α-olefin / (α-olefin) represented by the following general formulas (3) and (4)
A non-conjugated polyene random copolymer rubber was used.

Embedded image (In the formula, x is an integer of 0 to 10, R ³ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

Embedded image (In the formula, R ⁵ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.) In order to impart flexibility and tackiness to the sheet, the following general formula (5) [(CH ₂ —CH _{2 ) X - (CH 2 -CRH)} Y] P (5) ( wherein, R is an alkyl group represented by _{C W H 2W + 1, X} , Y, P, W is an integer, usually X Is 1 to 10
0, Y is 5 to 100, P is 5 to 500, and W is 1 to 10. The polymers having different viscosities shown in ()) were used.
The following shows the ingredients of the compounding ingredients.

Description of Raw Materials 1) Matrix component: ethylene / α-olefin / non-conjugated polyene random copolymer EPT-PX055 (Mooney viscosity (100 ° C.) 8, ethylene content 58% by weight, trade name of Mitsui Chemicals, Inc.) EPT-4010 (Mooney viscosity (100 ° C.) 8, ethylene content 65% by weight), trade name EPT-4021 manufactured by Mitsui Chemicals, Inc. (Moony viscosity (100 ° C.) 24, ethylene content 67% by weight), Mitsui Chemical name EPT-X3012P (Mooney viscosity (100 ° C) 1)
5, ethylene content 70% by weight), trade name of Mitsui Chemicals, Inc. 2) Matrix component: ethylene / α-olefin copolymer Lucant HC40 (viscosity 350 cSt (25 ° C.)),
Mitsui Chemicals Co., Ltd. product name HC3000X (viscosity 25000 cSt (25 ° C)),
Mitsui Chemicals Co., Ltd. product name HC10 (viscosity 140 cSt (25 ° C.)), Mitsui Chemicals Co., Ltd. product name 3) Thermal softening component: α-olefin dialen 30 (n = 30 to 40), Mitsubishi Chemical Corporation Product name Dialen 208 (n = 17 to 25), Mitsubishi Chemical Corporation
4) Thermal conductive filler: Alumina powder, AS30, trade name of Showa Denko KK 5) Thermal conductive filler: Aluminum nitride powder, UM, trade name of Toyo Aluminum Co., Ltd. 6) Thermal conductivity Filler: silicon carbide powder, GP # 1000,
7) Electromagnetic wave absorbing filler: Fe-Cr (metallic soft magnetic spherical powder), PMIC-15, trade name of Daido Steel Co., Ltd. 8) Electromagnetic wave absorbing filler: Fe-Cr (metallic soft magnetic flat powder), PMIC-15F, trade name of Daido Steel Co., Ltd. 9) Electromagnetic wave absorbing filler: Mn-Zn ferrite (oxide soft magnetic flat powder), BSF547 10) Electromagnetic wave absorbing filler: Fe-Ni (metallic soft magnetic spherical powder), MHT Permalloy PC, Mitsubishi Steel Corporation 11) Electromagnetic wave absorbing filler: Fe -Cr-Si (metal-based soft magnetic spherical powder), MHT410L-3Si, trade name of Mitsubishi Steel Corp. 12) Powder surface treatment agent: carbon functional silane, KBM-3103, product of Shin-Etsu Chemical Co., Ltd. Name

Preparation procedure of heat-softening electromagnetic wave absorbing heat radiation sheet
And raw materials of formulations shown in performance Evaluation 5,6 were charged into a planetary mixer and stirred for 2 hours mixing at 100 ° C.. Next, the mixture was degassed and mixed with two rolls at room temperature, and the obtained compound was extruded into a sheet having a width of 100 mm and a thickness of 0.5 mm using an extruder.

The obtained heat-softening sheet was punched and formed into a predetermined shape, and the noise attenuation rate, heat conductivity, heat resistance, viscosity and heat softening point were measured in the same manner as in Example 1.
Further, sheet workability, flexibility, tackiness, and handleability were evaluated in the same manner as in Example 1. The results are shown in Tables 5 and 6.

[0074]

[Table 5]

[0075]

[Table 6]

[Comparative Examples 5 to 8] Measurement results of physical properties and handleability test results of a silicone rubber heat dissipation sheet (0.5 mm thick (Comparative Examples 5 to 7)) and grease (Comparative Example 8) which are commercially available for comparison. Are shown in Table 7.

[0077]

[Table 7]

From the above results, the heat-softening electromagnetic wave-absorbing heat radiating sheet of the embodiment of the present invention has a contact heat resistance reduced to a negligible level as compared with a silicone rubber heat radiating sheet having the same thermal conductivity. As a result, the heat resistance was reduced, so that it was confirmed that the device had excellent heat dissipation performance, and that it was effective in heat dissipation of electronic components. Further, it was confirmed that the noise attenuation rate was high and the electromagnetic wave absorption performance was excellent.

[0079]

According to the present invention, it is possible to obtain an electromagnetic wave absorbing heat conductive composition having excellent heat radiation performance and excellent electromagnetic wave absorbing properties, and a heat softening electromagnetic wave absorbing heat radiating sheet formed from the composition.

[Brief description of the drawings]

FIG. 1 is a block diagram of a noise attenuation amount measuring method.

FIG. 2 is an explanatory diagram of a method of evaluating tackiness.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anechoic chamber 2 PC 3 Receiving antenna 4 Display 5 Keyboard 6 Shield room 7 EMI receiver (spectrum analyzer) 11 Heat sink 12 Heat dissipation sheet

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ikuo Sakurai 1-10 Hitomi, Matsuida-cho, Usui-gun, Gunma Prefecture Inside Silicon Electronics Research Laboratory, Shin-Etsu Chemical Co., Ltd. (72) Akihiro Suzuki, Matsuida-cho, Usui-gun, Gunma Prefecture 1-10 Hitomi, Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory (72) Inventor Kunihiko Mita 1-10 Hitomi, Matsuida-cho, Usui-gun, Gunma Prefecture F-term in Silicon Electronic Materials Research Laboratory, Shin-Etsu Chemical Co., Ltd. Reference) 4G002 AA04 AA06 AA11 AE02 4J002 BB021 BD121 BD161 BG031 CP031 DC006 DE116 FD206 GQ00 5E040 AA11 AB03 AB04 CA13 5E321 BB32 BB51 BB53 BB55 BB57 BB60 GG11 GH03 5F036 AA11 BB21 BD01

Claims (16)

[Claims] 1. A heat conductive composition for forming an electromagnetic wave absorbing heat radiation member disposed between a heat generating electronic component serving as an electromagnetic wave generation source and a heat radiation component, and generates heat by operation to become a temperature higher than room temperature. It is non-flowable at room temperature before the operation of the electronic component, and the heat generation during the operation of the electronic component lowers the viscosity, softens or melts, and at least the surface is fluidized, so that the electronic component and the heat radiating component An electromagnetic-wave-absorbing heat-conductive composition characterized by being filled with substantially no voids. 2. The electromagnetic wave absorbing heat conductive composition according to claim 1, wherein the heat generating electronic component generates and generates electromagnetic waves by applying a voltage. 3. The electromagnetic wave absorbing heat conductive composition according to claim 1, which is curable by a crosslinking reaction. 4. An organic binder component and an electromagnetic wave absorbing filler or an electromagnetic wave absorbing filler and a heat conductive filler as main components, wherein the temperature at which viscosity is reduced, softened or melted is 40 ° C. or more, 4. The electromagnetic wave absorbing heat conductive composition according to claim 1, wherein the temperature is not higher than the highest temperature due to heat generation of the component. 5. The electromagnetic wave absorber according to claim 4, wherein the organic binder component contains at least one selected from a siloxane polymer, an acrylic polymer, a polyolefin polymer, and a fluorine polymer. Heat conductive composition. 6. The at least one electromagnetic wave absorbing filler selected from a metal-based ferromagnetic powder and an oxide-based ferromagnetic powder.
The electromagnetic wave absorbing heat conductive composition according to claim 4, wherein the composition is a seed. 7. The electromagnetic wave absorbing heat conductive composition according to claim 6, wherein the metal-based ferromagnetic powder is at least one selected from iron and an alloy containing iron. 8. The ferromagnetic iron alloy is made of an Fe—Ni alloy, Fe
-Co system, Fe-Cr system, Fe-Si system, Fe-Al
System, Fe-Cr-Si system, Fe-Cr-Al system, Fe-
Al-Si system, Fe-B-Si system, Ni-Fe system, Co
The electromagnetic wave absorbing heat conductive composition according to claim 7, wherein the composition is at least one selected from the group consisting of -Fe-Ni-Si-B magnetic alloys. 9. The oxide-based ferromagnetic powder is at least one selected from ferrite.
The electromagnetic wave absorbing heat conductive composition according to the above. 10. The ferrite is made of ZnFe ₂ O ₄ , MnF.
_{e 2 O 4, MgFe 2 O} 4, CoFe 2 O 4, NiFe 2 O 4,
CuFe ₂ O ₄ , Fe ₃ O ₄ , Cu-Zn-ferrite, N
The electromagnetic wave-absorbing heat conductive composition according to claim 9, wherein the composition is at least one selected from i-Zn-ferrite and spinel-type ferrite having a basic composition of Mn-Zn-ferrite. 11. The ferrite is made of Ba ₂ Co ₂ Fe.
₁₂ O ₂₂ , Ba ₂ Ni ₂ Fe ₁₂ O ₂₂ , Ba ₂ Zn ₂ Fe
₁₂ O ₂₂ , Ba ₂ Mn ₂ Fe ₁₂ O ₂₂ , Ba ₂ Mg ₂ Fe
₁₂ O ₂₂ , Ba ₂ Cu ₂ Fe ₁₂ O ₂₂ , Ba ₃ Co ₂ Fe ₂₄ O ₄₁
Ferrox Sprayer (Y type, Z type)
The electromagnetic wave absorbing heat conductive composition according to claim 9, wherein the composition is at least one selected from type hexagonal ferrite. 12. A ferrite comprising BaFe ₁₂ O ₁₉ , Sr
Fe ₁₂ O ₁₉ and / or BaFe ₁₂ O ₁₉ , SrFe ₁₂ O ₁₉
Fe element of Ti, Co, Mn, Cu, Zn, Ni, M
at least one selected from the group consisting of magnetoplumbite (M-type) hexagonal ferrites having a basic composition replaced by g
The electromagnetic wave absorbing heat conductive composition according to claim 9, which is a seed. 13. The electromagnetic wave absorbing heat according to claim 4, wherein the heat conductive filler is at least one selected from non-magnetic metals, metal oxides, metal nitrides, and silicon carbide. Conductive composition. 14. A thermal conductivity of 0.5 W / mK or more and a viscosity at 80 ° C. of 1 × 10 ² to 1 × 10 ⁵ Pa ·
The electromagnetic wave absorbing heat conductive composition according to any one of claims 1 to 13, wherein the composition is s. 15. A heat-softening electromagnetic wave-absorbing heat-dissipating sheet, wherein the electromagnetic wave-absorbing heat-conductive composition according to claim 1 is formed in a sheet shape. 16. The electromagnetic wave-absorbing heat as claimed in claim 1, wherein the device generates heat by operating to have a temperature higher than room temperature, and is located between the heat-generating electronic component serving as an electromagnetic wave generation source and the heat-radiating component. By disposing a conductive composition and operating the heat-generating electronic component to generate heat, the composition is reduced in viscosity, softened or melted to fluidize at least its surface, and the heat-generating electronic component is radiated to the heat-generating electronic component. A method for applying an electromagnetic-wave-absorbing heat-conducting composition, characterized in that the composition is pressed from at least one of the components to fill the space between the electronic component and the heat-dissipating component with substantially no gap.